Uranium-titanium-niobium alloys



United States Patent 2,990,274 URANIUM-TITANIUM-NIOBIUM ALLOYS ShermanGreenberg, Chicago, Ill., assignor to the United States of America asrepresented by the United Slates Atomic Energy Commission No Drawing.Filed June 16, 1958, Ser. No. 742,446 1 Claim. (Cl. 75-122.7)

The present invention is concerned with uranium-base alloys and moreparticularly relates to uranium-base alloys containing titanium andniobium.

Uranium is not resistant to corrosion; therefore one object of thepresent invention is to so improve the properties of uranium anduraniumrich alloys as to enhance the corrosion resistance thereof andrender the same useful for various purposes for which uranium anduranium alloys now in use are not satisfactory or eiricient.

Still another object of this invention is to produceuranium-titanium-niobium alloys, which are useful as fuel elements innuclear reactors, such as disclosed in U.S. Patent No. 2,708,656 toFermi et al.

Other objects and advantages of the present invention will be apparentfrom the following description, taken in connection with the appendedclaim.

The present invention is directed to a ternary alloy of uranium,titanium and niobium, particularly one containing from about 2 /2 to 6wt. percent titanium and about 1 to 2. wt. percent niobium. Our testsindicate that the optimum composition of the alloy for use in a nuclearreactor is about 3 wt. percent titanium and 1 /2 wt. percent niobium.

In Patent No. 2,743,174 it is shown that binary alloys of uranium andtitanium are much more resistant to corrosive attack by water than isuranium alone. I have found that the addition of a relatively smallamount of niobium to the binary alloy described in the patent improvesgreatly its resistance to corrosion and that the ternary alloy maintainsits integrity many times longer than does an alloy containing noniobium.

The following chart illustrates the advantages obtained by the newalloys.

after an relapse of at least twice the time in which the binary alloyfailed.

It is believed that the samples of ternary alloy remain intact becausethe niobium acted to prevent damage by corrosion product hydrogen,thereby preventing formation of cracks.

Below about 2 /2% titanium the alloy has appreciably poorer corrosionresistance than with a higher amount. Above 6% titanium the corrosionresistance is probably satisfactory, but the alloy becomes brittle andtherefore unsuitable for use in a reactor. Optimum percentage of niobiumis about 1 /2% niobium, although amounts ranging from 1 to 2% areoperative to obtain the results desired.

The chart also shows that the alloy according to the present inventionis much more resistant to corrosion than is the ternary alloy containing5% zirconium and 1 /2% niobium, which is used in fuel elements for theExperimental Boiling Water Reactor at Argonne National Laboratory.Corrosion of that alloy was about 10 times greater than that of theternary alloy containing titanium.

The chart also shows the heat treatment to which each alloy wassubjected. A comparison between the results shown for the alloyaccording to my invention with several different heat treatments and thezirconium-containing alloy with about the same heat treatments indicatesthat my alloy is much less sensitive to heat treatment than is thezirconium-containing alloy. This statement also applies to the ternaryalloy as compared to the binary alloy.

These new alloys may be conveniently prepared by melting together therequired amounts of uranium, titanium and niobium in a suitablerefractory crucible, as for example a graphite crucible. Melting shouldbe in the absence of oxygen or moisture, as for example in v-acuo, andheating may be by inductive heating which facilitates mixing of themetals.

It will be understood that this invention is not to be limited to thedetails given herein, but that it may be modified within the scope ofthe appended claim.

What is claimed is:

An alloy which is resistant to corrosion by water at Temp., 1 CorrosionComposition 0. Time rate. mg./ Remarks cmfl/day U- 3% Ti 1 260 Samplefailed in 10 to 20 Sample failed by cracking.

l-2 wee s. U3% Ti 2 260 Sample broken into several pieces. U%% Ti-1%% Nb1 150 In view of result, no test was made at 260 C. 150 15.7 days 0 I ILT-3% Til} Nb 1 260 Tests continuing 1 Sample in excellent condition atafter 40 days. this time. U-3% Tl-1%% Nb 2 260 Tests continuing 1 Do.

after 5 days. U3% Ti- 136% Nb 5 260 Tests continuing 10 Sample inexcellent condition.

after 22 days. 150 10.4 days 0 U6% Tl1%% Nb 1 260 1.7 days 80 Testsample was beginning to crack when test was discontinued. U5% Zr1%% Nb 1200 One month 10 to 15 sampletihcrnmbling after about one mon U5% Zr-l%%Nb 2 260 Two months 6 Cracking atnld chipping after about one mon U5%Zr1} Nb 4 260 Up to 14 days"..- 17-30 Clifikillg develops in from 5 to14 ays.

1 Quenched from 1000 C.

1 Quenched from 1000 0.; aged 400 C.2 hours. quenched from 750 C.

4 Quenched from 725-750 0.

260 C. containing 3 weight percent titanium and 1 /2 weight percentniobium, the remainder being uranium, which alloy has been quenched froma temperature from 750 C. to 1000" C.

(References on following page) A comparison between the results shownfor the binary alloy and the 3% titanium ternary alloy at 260 C.indicates at once the great advantage of the ternary alloy. Thecorrosion rate is reduced to a tenth of that of the binary alloy and thesample is still in good condition 2,990,274 3 V 4 References Cited inthe file of this patent OTHER REFERENCES UNI BMI-971 CorrosionEvaluation of Binary Uranium A1- TED STATES PATENTS loys in Water at 100C., U.S. AEC, Oak Ridge, Tenn.,

2,743,174 Keeler et at 24, 1956 December 1954, pages 17-20. (Copy inScientific Li- 2,888,343 McGeary et a1 May 26, 1959 5 bury)WAPD-PWR-PMM-601, Document pu-bl. by Atomic FOREIGN PATENTS EnergyComm., February 1, 1956, page 10. Copy in 537,159 Canada Feb. 12, 1957 I75/122.7.

